Many footwear brands overlook how a slight material change results in big changes to the overall fit of the shoe. This article covers how the fit changes by using different materials in shoes.

Using the same last but different materials can change the fit by >1 size.

Shoes made using the same last, at the same factory, by the same brand with slight material modifications can fit up to 1 full size differently. SmartLast tested shoes show slight changes in the heel fit and much bigger fit difference in the front of the shoe in this situation. The biggest difference is in the ball of the foot, followed by the toe box width and length. These are key fit comfort areas that consumers feel.

Changing the stretch of a knit or mesh upper is the most common cause for material fit changes. We’ve seen big fit changes by something as small as adding 1 more color to a knit upper. Changes to toe cap and heel counter hardness also cause perceivable changes in fit. Some materials are more difficult to work with at the factory, causing inconsistent fit across a batch of sample or production shoes–this is a material fit issue that amplifies a workmanship issue. For all of these examples, human fit testing will not give you the accuracy you need to quantify and fix the problem.

Shoes with a waterproof liner fit tighter and shorter than their non-waterproof versions.

Waterproof shoes are the biggest cause for fit inconsistencies for a brand.  This is true even when last modifications are made for the waterproof bootie. On average, shoes that have a version that is waterproof and non-waterproof, the waterproof version fits ½ size tighter in the ball of the foot and toes, and ¼ size shorter in the toe box length. Why would this change occur?

More important than the thickness of the waterproof barrier is how stiff the material is. We refer to this as how “dynamic” the upper material is. A dynamic material will contour around your foot easily, while a less dynamic or stiff material will not. If you are using a stiff synthetic leather (not very dynamic) a waterproof barrier will not change the dynamic nature of the material. However, knits, wovens, and even soft suede are less dynamic when waterproofing is added. Quantified data on fit of your shoe will let you know how much your waterproof shoe fits differently than your other styles, allowing you to fix the materials, patterns, or last for optimal fit.

SmartLast helps your brand by providing fast, accurate data on fit with recommendations to optimize your fit. Contact us today to learn more about how materials are impacting your shoe’s fit.